Local Anesthesia

Question 1

Which is harder to block myelinated or non-myelinated?

Answer 1

non-myelinated

Question 2

Block is proximal to distal for peripheral fibers, so how does it go with core and mantle?

Answer 2

mantle–>core

Question 3

Out of the alpha category which is the easiest to block?

Answer 3

gamma

Question 4

Which is the easiest fiber to block overall?

Answer 4

B fibers

Question 5

What are the first signs you see that a spinal/epidural anesthesia is working vs the first signs you see that a peripheral nerve block is working?

Answer 5

spinal/epidural
-pain–>sensory–>motor

peripheral
-first sign may be lack of proximal muscle coordination

Question 6

What type of states of the voltage gated ion channels do local anesthetics prefer to bind?

Answer 6

-inactivated and open rather than resting

Question 7

Where do local anesthetics bind?

Answer 7

-R site

Question 8

What type of anesthetics can cross the membrane what type can bind the active site?

Answer 8

• uncharged-cross

- charged-bind

Question 9

What determines onset time?

Answer 9

pH and pKa

Question 10

What determines potency?

Answer 10

Lipid solubility

Question 11

What determines duration?

Answer 11

protein binding

-local tissue proteins-can bind create a sink that slowly released into the nerve-more binding longer they will last

Question 12

How can you change onset time?

Answer 12

raise the pH of the solution by adding sodium bicarbonate

-use a drug with a lower pKa

Question 13

What types of drugs is the vasoconstricting power of epinephrine most useful for?

Answer 13

Drugs not highly protein bound like:

Lidocaine, Mepivicaine

Question 14

What types of drugs is the vasoconstricting power of epinephrine less useful for?

Answer 14

Highly protein bound drugs

-ropivacaine, bupivacaine

Question 15

What can IV lidocaine treat?

Answer 15

arrthymias

Question 16

Where do you give spinal anesthesia?

Answer 16

L3-5 injection

• subarachnoid block
• drug deposited around cauda equina

Question 17

What level do you give epidural?

Answer 17

any level

• volume dependent segmental blockade
• concentration effects blook quality
• site of action is nerve roots
• not inside dura

Question 18

How does a blockade of thoracic level affect breathing?

Answer 18

• tidal volume normal
• minimal reduction in vital capacity with abdominal paralysis
• loss of proprioception can be upsetting to patient

Question 19

If there was respiratory arrest with a high spinal block what would be the cause, what would you do?

Answer 19

• hypoperfusion of respiratory center in the 4th ventricle
• NEVER because of paralyzed phrenic nerves

treat with vasopressors and supportive ventilation

Question 20

How do neuraxial anesthetics affect vascular beds?

Answer 20

dilation

Question 21

What happens to the heart during neuraxial anesthesia?

Answer 21

brady-unopposed vagal stimulation-decreased venous return-bezold-jarisch reflex
-cardioaccelerator fibers: t1-4 blocked

Question 22

What does absorption of the drug depend on?

Answer 22

• vascularity
• properties of the drug
• properties of the patient
• renal-increased blood flow-increased absorption
• more acidotic more unchanged so more easily absorbed
• additional vasoconstrictors

Question 23

Which is more easily affected neuro or cardio?

Answer 23

neuro

Question 24

WHat do you do to treat cardiac toxicity with use of local anesthetic?

Answer 24

intralipid

-creates a sink that LA can be sequestered into

Question 25

What is a post dural puncture headache?

Answer 25

- frontal or occipital - positional - photophobia/ phonophobia - may have neurological deficits Treatment fluid, analgesics, caffeine, blood patch

Question 26

What causes type 1 or type 4 hypersensitivity?

Answer 26

esters | -paba